Studies with Radioactive Tracers in Plant Nutrition: II. THE ESTIMATION OF RADIOACTIVE TRACERS

Part I Tracer methods can yield valid results only if the behaviourof the tracer within the plant is indistinguishable from thatof the normal element. The extent to which radioactive isotopessatisfy this requirement must be considered from the followingviewpoints:

1. their chemical and physical bahaviour before disintegration;
2. the effects and substances formed by their disintegration;
3. the effects of the radiation they emit.

Whereas, chemically and physically, isotopes with the exceptionof H¹ and H³ satisfy this requirement, they may cause significantradiation damage even when supplied in low concentration ifthey are accumulated metabolically. The investigation of possibleradiation effects is therefore an essential preliminary to allphysiological investigations. The value of tracer methods is considered. Part II Equipment and laboratory procedures for the electronic assayof P³² are described. For the assay of samples containing P³²a wet ashing method and the subsequent use of a liquid countingtube is preferred. Improvements of equipment to suit the requirementsof plant nutritional studies are considered. Sources of experimentalerror are examined. On account of the decay of radioactive isotopes,the time factor may be of special importance in tracer work.Its effect on both experimental design and on laboratory proceduresis considered. It is stressed that the scope and replicationof large experiments, particularly if they are of long duration,may be subject to serious limitations. The importance of simplifyingthe equipment used in tracer assay and increasing its reliabilityis emphasized.     

酸度和铝对马尾松生长的影响

用溶液培养法研究了铝对马尾松 ( Pinus massoniana)幼苗生长的影响。马尾松耐酸性较强 ,在 p H为 3.5— 5 .5范围内均能正常生长。马尾松对铝中度敏感 ,在 p H4 .0条件下 ,铝毒害的阈值浓度为 4 .0 ppm。铝在溶液中存在的状态依 p H值而变化 ,不同形态的铝离子对马尾松的毒性不同 :Al3 的毒性大于 Al( OH) 2 和 Al( OH) 2 。极低浓度 ( <0 .1 5 mmol/L)的 Al3 对马尾松生长有刺激作用。 Ca2 对 Al3 的毒性有拮抗作用 ,对马尾松产生抑制作用的 Al/Ca摩尔比小于 1     

COMPARATIVE STUDIES ON RESPIRATION : III. THE EFFECT OF ETHER ON THE RESPIRATION AND GROWTH OF BACILLUS SUBTILIS.

1. In all the concentrations of ether studied (from 0.037 to 7.3 per cent) there is an increase in the rate of respiration of Bacillus subtilis followed by a decrease. 2. In 7.3 per cent ether in tap water there is an extraordinary increase in the output of CO₂ (amounting to 50 times the normal). This does not occur when 0.85 per cent NaCl is added, which indicates antagonism between ether and NaCl. 3. Ether is toxic in low concentrations (0.037 to 1.1 per cent) and high concentrations (3.65 to 7.3 per cent) but in intermediate concentrations (1.1 to 3.65 per cent) stimulates growth.     

EFFECT OF 4'-CHLOROGLUTARANILIC ACID ON GROWTH AND DEVELOPMENT OF SUNFLOWER SEEDLINGS

The potential growth-regulating properties of 4'-chloroglutaranilic acid (CGA) as well as oxygen and nitrogen isosteres were examined in whole-plant bioassay systems utilizing sunflower seedling (Helianthus annuus L.). Test systems included both soil-grown plants and hydroponic studies. Foliar applications of CGA produced growth inhibition which was detectable within 24 hr and which persisted for at least 30 days. Direct application to roots produced a growth inhibition which was 15% greater than foliar applications. Foliar or root application at 10^-5 m or greater concentrations produced gross changes in leaf morphology. Total plant-height inhibition was principally associated with stem growth in an area located between primary leaves and the shoot meristem. CGA was found to be 32 % less active than IAA as a growth promoter, but was 76 % more active than IAA as a growth inhibitor; the most severely affected organ was the leaf and the least affected was the root system. Leaves from soil-grown plants treated wth a 10^-3 m foliar application of CGA possessed several abnormalities. These included an increase in thickness and dry weight, a reduction in chloroplast starch vacuoles, extractable starch, soluble hexoses, and soluble proteins.     

The Uptake of Phosphate by Plants from Flowing Nutrient Solution: III. EFFECT OF CHANGED PHOSPHATE CONCENTRATIONS ON THE GROWTH AND DISTRIBUTION OF PHOSPHATE WITHIN PLANTS OF LOLIUM PERENNE L.

Perennial ryegrass (Lolium perenne L.) was grown from seed for29 d in flowing solution culture containing 0.1, 0.4 or 6.4mmol m^–3 P before the concentrations were changed (0.1and 0.4 raised to 6.4; 6.4 lowered to 0.4; controls unchanged)for an experimental period of two weeks to test the hypothesisthat after the seedling stage, the maximum rate of plant growthcould be sustained by a lower concentration of phosphate atthe root/solution interface than was necessary for the maximumrate of seedling growth. During the 29 d seedling period growthwas greatest on 6.4 mmol m^–3 P achieving 179 mg per plantdry weight compared with 122 and 26 mg on 0.4 and 0.1 mmol m^–3P respectively. During the experimental period growth on thetreatment 6.4 lowered to 0.4 mmol m^–3 P continued at thesame rate as the 6.4 control achieving 981 and 983 mg per plantdry weight respectively. Similarly growth of the treatment 0.4raised to 6.4 mol m^–3 P was unaffected by the change inconcentration and was comparable with the 0.4 control. Bothresults support the hypothesis for seedlings exceeding about100 mg per plant dry weight. In contrast the small plants ofthe treatment 0.1 raised to 6.4 mmol m^–3 P behaved similarlyto seedlings and responded rapidly to the increased concentrationof phosphate in solution, achieving high rates of phosphateuptake and increasing the growth of shoot more than the growthof root so that the ratio of root: shoot declined from 065 to0.34, a value similar to that for the seedlings grown on 6.4mmol m^–3 P. Key words: Lolium perenne L, Phosphate concentration, Seedling growth     

电离辐射对伤口巨噬细胞生长因子基因表达的影响及苯妥因钠的作用

研究了电离辐射全身和局部照射对伤口巨噬细胞(MΦ)生长因子基因表达的影响及苯妥因钠的作用。伤口MΦ从置入大鼠背部的聚乙烯醇海绵中收集,用原位杂交技术测定血小板源性生长因子-B(PDGF-B)和转化生长因子-β(TGF-β_1)mRNA在MΦ表达的阳性细胞率。结果表明,6Gy全身辐射后伤口MΦ PDGF-B和TGF-β_1 mRNA阳性表达率明显下降,20Gy局部辐射后无明显影响;苯妥因钠对正常伤口、全身辐射和局部辐射后的伤口MΦ PDGF-B和TGF-β_1 mRNA表达的阳性率都有明显的提高。这说明伤口MΦ生长因子基因表达的降低与全身辐射后创伤愈合延迟有关;苯妥因钠明显增加伤口MΦ生长因子基因表达而有利于创伤愈合。     

Growth Inhibition Studies: I. MEASUREMENT OF THE EFFECTS OF INHIBITORS ON THE GROWTH RATE OF FLAX SEEDLINGS

A method for measuring the rate of growth of small seedlingsunder special conditions suitable for inhibition and reversalstudies is described, and its use is illustrated in studiesof the inhibitory action of a variety of chemical substances. The limitations imposed, in such studies, by the osmotic pressureof the test solutions have been examined in the case of flaxseedlings.     

THE EFFECT OF AGITATION AND TURBULENCE OF THE GROWTH MEDIUM ON THE GROWTH AND VIABILITY OF MICROCYSTIS

SUMMARY

Observation of natural blooms of Microcystis, suggested that increased turbulence plays a role in retarding bloom formation of Microcystis. In laboratory experiments the influence of turbulence mediated by a magnetic stirrer on the growth and viability of Microcystis in batch cultures was determined. The different turbulences (0, 25, 75, 126, 209 and 314 cm sec^?1 linear velocity) had no effect on the growth rate. There was a highly significant correlation between the linear velocity and percentage viability as determined by a plating and serial dilution method. The viability ranged from 0,8% for stationary cultures to 99,2% for vigorously stirred (314 cm sec^?1 linear velocity) cultures.     

The Role of Boron in Plant Growth: II. THE EFFECT ON GROWTH OF THE RADICLE

Estimates of cell number, cell volume, respiratory rate, nitrogen,sugar, and nucleic acid content were made on 1 mm. sectionsof the radicles of field bean at frequent intervals during thefirst 96 hours of growth in nutrient solutions with and withoutboron. The primary effects of deficiency were cessation of cell divisionand enlargement of the apical cells. The increased volume ofthe apical cells may have been due to either a longer periodbeing available for development as the rate of mitosis decreased,or to an unusually rapid rate of cell extension. The resultsindicated that cell division did not cease for lack of availablesugar nor as a result of failure to synthesize protein or nucleicacids. It is suggested that in the absence of boron divisionceases because abnormalities in the formation of the cell wallprevent the cell from becoming organized for mitosis. In particularthe hypothesis that boron is concerned with the formation of‘pectin’ from uridinediphosphate-D-glucose is examinedin the light of published evidence.     

Myrosinase in Brassicaceae (Cruciferae): III. EFFECT OF ASCORBIC ACID ON MYROSINASES FROM SINAPIS ALBA L. SEEDLINGS

The effect of L-ascorbic acid (AA) on myrosinase activity wasstudied in white mustard, Sinapis alba L. Enzyme extracts wereprepared from different organs of dark- and light-grown seedlings.The highest activation caused by AA was found for myrosinasefrom light-grown primary roots. The activation level was morethan 12 times higher than that of the control. The maximum activationgenerally occurred at 1–10 mM AA, and in the case of myrosinasefrom light-grown hypocotyls even at 50 mM AA. The myrosinasesfrom cotyledons were least affected by addition of AA. To studythe effect of AA on different isoenzymes of myrosinases, theisoenzymes were separated on polyacrylamide gels. When the gelswere incubated in an AA solution, after electrophoresis differenceswere found in the activation of isoenzymes of different myrosinases.     

Growth and Development in the Young Tomato: III. THE EFFECT OF NIGHT AND DAY TEMPERATURES ON VEGETATIVE GROWTH

Tomato seedlings were grown in a 12-hour day at constant andalternating day and night temperatures ranging from 10°to 30° C. The pattern of results was similar at light intensitiesof 400 and 800 f.c. The maximum rate of dryweight accumulationoccurred at a constant temperature close to 25° C. The effectsof day and night temperatures on total dry weight showed a considerabledegree of independence. The optimum day temperature was 25°C irrespective of the night temperature; the optimum night temperatureincreased from 18° to 25° C over the whole range ofday temperature. On average, day temperature affected totaldry weight twice as much as night temperature. High night temperaturesto some extent compensated for low day temperatures. The optimumday and night temperatures for leaf growth were both 25°C. On average day temperature affected leaf growth one and ahalf times as much as night temperature. By 12-hourly sampling it was shown that the cotyledons and leavesgrow throughout both day and night and that high night temperatureaccelerates nocturnal growth (cotyledons by cell expansion,young leaves by cell multiplication). Plants having receivedonly one night at 25° C, as compared with 15° C, showa slightly greater assimilation during the following light period,apparently as a consequence of increased photosynthetic surface.The respiratory loss in dry weight during darkness was not significantlyaffected by temperature over the range 15–25° C.     

(2 CHLOROETHYL) TRIMETHYLAMMONIUM CHLORIDE AND RELATED COMPOUNDS AS PLANT GROWTH SUBSTANCES. III. EFFECT ON GROWTH AND FLOWERING OF THE TOMATO

Wittwer, S. H., and N. E. Tolbert. (Michigan State Univ., E. Lansing.) (2-Chloroethyl) trimethylammonium chloride and related compounds as plant growth substances. III. Effect on growth and flowering of the tomato. Amer. Jour. Bot. 47(7) : 560–565. Illus. 1960.—Application of 10^–3 to 10^–7 M solutions of (2-chloroethyl) trimethylammonium chloride, (2 bromoethyl)-trimethylammonium bromide, or (2,3-n-propylene) trimethylammonium bromide to the roots of the tomato plant markedly altered growth and promoted earlier flowering. Treated plants developed thicker stems, and dark-green, savoyed leaves. The growth changes were similar to those produced by exposure to high light intensities and low temperatures, and were opposite to, and more persistent than, those induced by gibberellin. A stepwise regulation in the magnitude of growth and dry matter accumulation in tomato plants followed application of chemicals of increasing concentration to cultural solutions. This growth response varied from a stimulation at 10^–7 M to a marked suppression at 10^–4 M without delay of flowering or visible injury. The control of growth and flowering by the use of these chemicals offers several practical possibilities for their utilization in tomato culture.